Cooling fan

ABSTRACT

A cooling fan includes a motor ( 30 ) for generating an airflow, and a housing ( 10 ) defining a space ( 40 ) for receiving the motor therein. The housing defines an air inlet ( 57 ) through which the airflow flows into the housing. The motor has a plurality of fan blades ( 31 ) extending radially outwards from a periphery thereof. The motor is mounted under the air inlet. The air inlet is so configured or positioned that the fan blades are unevenly exposed to an ambient air through the air inlet. The housing further has an air outlet ( 56 ) through which the airflow flows out of the fan. The air outlet is oriented perpendicular to the air inlet.

FIELD OF THE INVENTION

The present invention relates generally to a cooling fan, and more particularly to a design of an air inlet of a centrifugal cooling fan (blower) in order to improve performance thereof.

DESCRIPTION OF RELATED ART

With continuing development of the electronic technology, electronic packages such as CPUs are generating more and more heat that is required to be dissipated immediately. Conventional cooling fans are commonly used for cooling the CPUs and other heat-generating electronic components.

A conventional cooling fan typically can be classified into two types: axial fan and centrifugal fan (blower). The blower is more suitably used in a laptop computer since it has a flat configuration and a large air flow rate. A blower comprises a motor and a housing receiving the motor therein. The housing defines at least an air inlet and an air outlet. The inlet and outlet are oriented to be perpendicular to each other. An airflow generated by the motor flows into the housing via the air inlet and out of the housing through the air outlet. The motor comprises a stator and a rotor being rotatable with respect to the stator. The rotor includes a plurality of fan blades extending radially from an outer-periphery of the rotor and a shaft extending downwardly thereof. The stator includes a bearing ratatably receiving the shaft therein. The most direct and effective way to improve cooling and heat dissipation efficiency of the cooling fan (blower) is to increase the air flow rate thereof. Increasing the air flow rate can be achieved by different measures, for example, by increasing the revolution speed (i.e. rpm (revolutions per minute)) of the fan or by increasing the size of the fan.

Increasing the revolution speed of the fan increases the air flow rate of the fan; therefore, the cooling and heat dissipation effectiveness is relatively improved. However, increasing the revolution speed of the fan causes a bearing of the fan to wear quickly. Furthermore, heat produced by friction between a shaft and the bearing of the fan causes the bearing to be damaged quickly, resulting in short service life of the cooling fan. On the other hand, to increase the size of the fan is not practical since the computer industry has required the computer components to be smaller and smaller.

Furthermore, keeping the fan blades in balance is another important factor to be taken into account when wishing to increase the air flow rate by increasing the revolving speed of the fan. If the fan blades are not arranged in precise balance, the blades will vibrate when operating the cooling fan at a high speed, which affects the operation quality of the cooling fan and its service life. Nevertheless, a precise balance of the fan blades means a high manufacturing cost. Therefore, it is not a good idea to increase the air flow rate of the cooling fan simply by increasing the revolving speed of the fan blades. Further, increasing the revolving speed of the fan blades also results in consuming more power and increasing more heat.

Therefore, it is desired to design a blower which can increase the amount of airflow without either increasing the revolving speed of the fan or increasing the size of the blower.

SUMMARY OF INVENTION

According to a preferred embodiment of the present invention, a cooling fan comprises a motor for generating an airflow, and a housing defining a space for receiving the motor therein. The housing defines an air inlet for enabling the airflow to enter the housing. The air inlet is circular and has a center. The center of the air inlet is laterally offset from a center of the motor. By such design, the airflow can be more smoothly drawn into the housing through the air inlet. Accordingly, air flow rate of the cooling fan is increased, whereby the cooling and heat dissipation efficiency of the cooling fan is improved.

Other advantages and novel features of the present invention will be drawn from the following detailed description of a preferred embodiment of the present invention with attached drawings, in which:

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an isometric, assembled view of a cooling fan in accordance with a preferred embodiment of the present invention.

FIG. 2 is an isometric, explored view of the cooling fan of FIG. 1;

FIG. 3 is similar to FIG. 1, but showing a second embodiment of the cooling fan;

FIG. 4 shows a third embodiment of the cooling fan; and

FIG. 5 shows a forth embodiment of the cooling fan.

DETAILED DESCRIPTION

Referring to FIGS. 1-2, a cooling fan according to a preferred embodiment of the present invention includes a housing 10 and a motor 30 received in the housing 10. The cooling fan is a centrifugal fan which is also called as a blower.

The housing 10 includes a base 20 and a cover 50 mounted on the base 20. Together the base 20 and cover 50 defines a space 40 for receiving the motor 30 therein. The base 20 is approximately planar and has a circular rear side. Four mounting portions 28 extend outwardly from the base 20 for securing the base 20 with the cover 50. The mounting portions 28 are arranged along a circumferential periphery of the base 20. Each mounting portion 28 defines a mounting hole 29 therein for extension of a fixing element (not labeled), such as a rivet. A protrusion 21 extends outwardly from a front edge of the base 20. A plurality of fins 22 is arranged on the protrusion 21. A flow channel 23 is defined between each two adjacent fins 22.

A central tube 24 extends upwardly from a central portion of the base 20 for supporting the motor 30 thereon. An opening 25 is defined in the base 20 around the central tube 24. The opening 25 is circular and has a center at A. The center A is laterally offset from a center of a curvature of the circular rear side of the base 20. Three ribs 27 connect the base 20 and the central tube 24, and separate the opening 25 into three portions.

The cover 50 includes a top wall 51 and a sidewall 53 extending downwardly from an outer-periphery of the top wall 51. The top wall 51 has a shape and size similar to the base 20. A circular shaped air inlet 57 is defined in the top wall 51 and communicates with the space 40 of the housing 10. The air inlet 57 has a center at B. The center B of the air inlet 57 is laterally offset from the center A of the opening 25 of the base 20. An ear 58 extends outwardly from the outer-periphery of the sidewall 53 for connection with a corresponding mounting portion 28 of the base 20. The ear 58 defines a through hole 59 for being aligned with the mounting hole 29 of the corresponding mounting portion 28. A flange 55 extends outwardly from a front edge of the cover 50 corresponding to the protrusion 21 of the base 20. Together the flange 55 and protrusion 21 define an air outlet 56 receiving the fins 22 therein. The air outlet 56 communicates with the air inlet 57 via the space 40 of the housing 10, and is perpendicular to the air inlet 57.

The motor 30 is received in the housing 10 and supported by the central tube 24. The motor 30 is located under the air inlet 57. The motor 30 is circular and defines a center at C. A plurality of fan blades 31 extends radially and outwardly from an outer-periphery of the motor 30. An outer edge of the fan blades 31 defines a circle V. A center of the circle V is coincidental with the center C of the motor 30 and the center A of the opening 25 of the base 20, but is laterally offset from the center B of the air inlet 57 of the cover 50.

During assembly, the cover 50 fixedly secures with the base 20 and together defines the space 40 therein. The fixing elements extend through the through holes 59 of the cover 50 and the mounting holes 29 of the base 20 to secure the cover 50 with the base 20. The motor 30 is received in the housing 10 and supported by the central tube 24. The center C of the motor 30 is laterally offset from the center B of the air inlet 57; thus, a distance between the circumference of the air inlet 57 and the center C of the motor 30 is various. Since the center of the circle V is coincidental with the center A of the opening 25, and the center A is laterally offset from the center of the curvature of the circular rear side of the base 20; thus, the center of the circle V is laterally offset from the center of the curvature of the circular rear side base 20. In this embodiment, the center of the circle V is located close to a left lateral side of the base 20 as viewed from FIGS. 1 and 2. Thus, a wedge-shaped interspace is defined between the inner surface of the sidewall 53 and the circle V. The distance between the inner surface of the sidewall 53 of the housing 10 and the circle V increases along the rotation direction of the motor 30. In this embodiment, the motor 30 rotates clockwise as viewed from FIG. 1.

During operation of the cooling fan, the protrusion 21 of the base 20 is thermally connected with a heat generating device (not shown). A power supply (not shown) provides a voltage to the motor 30 to drive the motor 30 to rotate. Then the rotary motor 30 brings an airflow flowing through the air inlet 57 into the housing 10. The fan blades 31 push the airflow flowing along the rotation direction of the motor 30, and finally form an airflow having a relatively larger amount and pressure. The airflow flows through the flow channels 23 of the fins 22 in the air outlet 56, and take away the heat of the fins 22 absorbed from the heat generating device. Since the center B of the air inlet 57 is laterally offset from the center C of the motor 30, the air inlet 57 and the motor 30 are not concentric to each other. By such design, the fan blades 31 are unevenly exposed to an ambient air through the air inlet 57, and the air can be more smoothly drawn into the space 40 via the air inlet 57 by the fan blades 31. Turbulence of the airflow generated at the air inlet 57 can be reduced. Thus, the flow loss of the airflow decreases, and finally improves the pressure and velocity of the airflow. Accordingly, the amount of airflow (or air flow rate) of the cooling fan is increased, and finally improves the cooling and heat dissipation efficiency of the cooling fan. The center B of the air inlet 57 is located near a right lateral side of the base than the center C of the motor 30 as viewed from FIG. 1.

FIG. 3 illustrates the cooling fan in accordance with a second embodiment of the present invention. Except for the air inlet 357 of the cover 350, other parts of the cooling fan in accordance with the second embodiment are substantially the same as the cooling fan of the previous embodiment. The air inlet 357 is noncircular, and has an elliptic shape. The center of the air inlet 357 is coincidental with the center C of the motor 30. Then the air inlet 357 has a shaped different from that of the motor 30. The fan blades 31 are unevenly exposed to the ambient air through the air inlet 357. Thus, the air inlet 357 can more smoothly guide the airflow flowing into the space 40 of the housing, and reduces the flow loss of the airflow and improves the amount of airflow. In a modification of this embodiment, the center B of the air inlet 357 can be laterally offset from the center C of the motor 30.

Referring to FIG. 4, it illustrates the cooling fan in accordance with a third embodiment of the present invention. Similar to the previous embodiments, the cooling fan also comprises the cover 450 having an air inlet 457 and the motor 30 received therein. The difference of the third embodiment over the previous embodiments is that the air inlet 457 is irregular shaped. The shape of the air inlet 457 is neither circular nor elliptic. By such design the fan blades non-uniformly exposed through the air inlet.

Referring to FIG. 5, in this embodiment the cooling fan having a pair of air outlets 556. The two air outlets 556 are perpendicular to the air inlet 557 of the cover 550 and perpendicular to each other. Thus, the airflow generated by the cooling fan is separated into two sub-flows which flow out the housing in two perpendicular directions through the outlets 556. Then the airflow can be sufficiently utilized to dissipate heat generated by the different devices arranged at different positions. In this embodiment, the geometry relationship between the air inlet 557 and the motor is the same as the first embodiment.

Each of the previous embodiments of the cooling fan defines a circular shaped opening 25 in the base 20 of the cooling fan. The center A of the opening 25 is coincidental with the center C of the motor 30. The opening 25 acts as a second air inlet for improving the air flow rate of the fan. The shape of the opening 25 can be various as circular, elliptic or irregular. Furthermore, the center A of the opening 25 may be laterally offset from the center C of the motor 30 as the center B of the air inlet 57 of the first embodiment.

It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present example and embodiment is to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. 

1. A cooling fan comprising: a motor for generating an airflow; and a housing defining a space for receiving the motor therein; wherein the housing defines a noncircular air inlet for air flowing into the housing therethrough when the motor is operated in a top wall thereof, and an air outlet for the air to leave the housing, the air inlet being oriented perpendicular to the air outlet, the housing having a front side, a rear side and two lateral sides between the front and rear sides.
 2. The cooling fan as claimed in claim 1, wherein a center of the air inlet is laterally offset from a center of the motor.
 3. The cooling fan as claimed in claim 1, wherein the air inlet is elliptic or irregular.
 4. The cooling fan as claimed in claim 1, wherein the housing comprises a cover defining the air inlet therein and a base for mounting the cover thereon, the base defines an opening parallel to the air inlet.
 5. The cooling fan as claimed in claim 4, wherein a center of the opening is laterally offset from the center of the motor.
 6. The cooling fan as claimed in claim 5, wherein the opening is elliptic or irregular.
 7. The cooling fan as claimed in claim 1, wherein the air inlet is located at the front side of the housing.
 8. The cooling fan as claimed in claim 7, wherein housing defines an additional air outlet at one of the lateral sides of the housing, the additional air outlet is oriented perpendicular to the air outlet and the air inlet.
 9. A cooling fan comprising: a motor having a plurality of blades for generating an airflow; and a housing defining a space for receiving the motor therein, the housing defining an air inlet therein; wherein a distance between a circumference of the air inlet and a center of the motor is various along a circumferential direction of air inlet.
 10. The cooling fan as claimed in claim 9, wherein the air inlet is noncircular.
 11. The cooling fan as claimed in claim 10, wherein the air inlet is elliptic or irregular.
 12. The cooling fan as claimed in claim 9, wherein a center of the air inlet is radially offset from a center of the motor.
 13. The cooling fan as claimed in claim 9, wherein the housing defines an air outlet perpendicular to the air inlet, and a plurality of fins is received in the air outlet of the housing.
 14. The cooling fan as claimed in claim 9, wherein the housing defines two air inlets at a front side and a lateral side of the housing, respectively.
 15. A cooling fan comprising: a hosing having a top wall, a rear side, a front side and two lateral sides between the rear side and the front side, an air inlet defined in the top wall through which air flows into the housing, and an air outlet through which the air leaves the housing, the air outlet being oriented perpendicular to the air inlet; and a motor rotatably received in the housing under the air inlet, having a plurality of fan blades extending radially outwardly from a periphery of the motor, when the motor rotates, the fan blades drawing the air into the housing via the air inlet and expelling the air out of the housing via the air outlet; wherein the fan blades are unevenly exposed to an ambient air through the air inlet.
 16. The cooling fan as claimed in claim 15, wherein the air inlet is circular and has a center, the motor is circular and has a center, the center of the air inlet is laterally offset from the center of the motor.
 17. The cooling fan as claimed in claim 15, wherein the air inlet is elliptic and has a center, the motor is circular and has a center, the center of the air inlet is coincidental with the center of the motor.
 18. The cooling fan as claimed in claim 15, wherein the air inlet is elliptic and has a center, the motor is circular and has a center, the center of the air inlet is laterally offset from the center of the motor.
 19. The cooling fan as claimed in claim 15, wherein the air inlet has an irregular shape.
 20. The cooling fan as claimed in claim 16, wherein the housing further has a second outlet, the second outlet is oriented perpendicular to the air inlet and the air outlet.
 21. The cooling fan as claimed in claim 16, wherein when the fan blades rotate along a clockwise direction as viewed from a top of the fan, the center of the air inlet is located near a right side of the housing than the center of the motor. 